Ceramic showerheads with conductive electrodes

ABSTRACT

Exemplary semiconductor processing chamber showerheads may include a dielectric plate characterized by a first surface and a second surface opposite the first surface. The dielectric plate may define a plurality of apertures through the dielectric plate. The dielectric plate may define a first annular channel in the first surface of the dielectric plate, and the first annular channel may extend about the plurality of apertures. The dielectric plate may define a second annular channel in the first surface of the dielectric plate. The second annular channel may be formed radially outward from the first annular channel. The showerheads may also include a conductive material embedded within the dielectric plate and extending about the plurality of apertures without being exposed by the apertures. The conductive material may be exposed at the second annular channel.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 16/245,698, filed Jan. 11, 2019, the contents of which are herebyincorporated by reference in their entirety for all purposes.

TECHNICAL FIELD

The present technology relates to semiconductor processes and equipment.More specifically, the present technology relates to ceramic chambercomponents that may operate as system electrodes.

BACKGROUND

Integrated circuits are made possible by processes which produceintricately patterned material layers on substrate surfaces. Producingpatterned material on a substrate requires controlled methods forremoval of exposed material. Chemical etching is used for a variety ofpurposes including transferring a pattern in photoresist into underlyinglayers, thinning layers, or thinning lateral dimensions of featuresalready present on the surface. Often it is desirable to have an etchprocess that etches one material faster than another facilitating, forexample, a pattern transfer process. Such an etch process is said to beselective to the first material. As a result of the diversity ofmaterials, circuits, and processes, etch processes have been developedwith a selectivity towards a variety of materials.

Etch processes may be termed wet or dry based on the materials used inthe process. For example, a wet etch may preferentially remove someoxide dielectrics over other dielectrics and materials. However, wetprocesses may have difficulty penetrating some constrained trenches andalso may sometimes deform the remaining material. Dry etches produced inplasmas formed within the substrate processing region can penetrate moreconstrained trenches and exhibit less deformation of delicate remainingstructures. However, plasmas may damage the substrate or chambercomponents through the production of electric arcs as they discharge, aswell as through bombardment and etching of system components.

Thus, there is a need for improved systems and methods that can be usedto produce high quality devices and structures. These and other needsare addressed by the present technology.

SUMMARY

Exemplary semiconductor processing chamber showerheads may include adielectric plate characterized by a first surface and a second surfaceopposite the first surface. The dielectric plate may define a pluralityof apertures through the dielectric plate. The dielectric plate maydefine a first annular channel in the first surface of the dielectricplate, and the first annular channel may extend about the plurality ofapertures. The dielectric plate may define a second annular channel inthe first surface of the dielectric plate. The second annular channelmay be formed radially outward from the first annular channel. Theshowerheads may also include a conductive material embedded within thedielectric plate and extending about the plurality of apertures withoutbeing exposed by the apertures. The conductive material may be exposedat the second annular channel.

In some embodiments, the second annular channel may be defined withinthe dielectric plate to a greater depth than the first annular channel.The conductive material may extend through the dielectric plate at adepth within the dielectric plate greater than the depth of the firstannular channel. The conductive material may be exposed by the secondannular channel without being exposed by the first annular channel. Theshowerheads may also include an RF gasket seated within the secondannular channel and configured to operate the conductive material as anelectrode. The showerheads may also include an elastomeric elementseated within the first annular channel. The conductive material mayinclude a foil or mesh extending across an interior area of theshowerhead defined by the first annular channel. The conductive materialmay include a plurality of tabs extending from the interior area of theshowerhead to the second annular channel.

Some embodiments of the present technology may also encompasssemiconductor processing chamber showerheads that may include a plateincluding a first dielectric material. The plate may be characterized bya first surface and a second surface opposite the first surface. Theplate may define a plurality of apertures through the plate. Theshowerheads may include a conductive material disposed on the firstsurface of the plate, and the conductive material may be maintained at afirst radial distance from each aperture of the plurality of apertures.The showerheads may also include a coating including a second dielectricmaterial. The coating may extend across the conductive material, and thecoating may be maintained at a second radial distance from each apertureof the plurality of apertures. The second radial distance may be lessthan the first radial distance.

In some embodiments, the conductive material may be exposed at a radialedge of the showerhead to provide electrical coupling of the showerhead.The showerhead may define an annular channel in the first surface of theplate radially outward of the plurality of apertures, and radiallyinward of the exposed conductive material at the radial edge of theshowerhead. The coating may be or include a multilayer coating. Thefirst dielectric material and the second dielectric material may be orinclude different materials. The conductive material may be or include aperforated foil or mesh.

Some embodiments of the present technology may encompass semiconductorprocessing chambers having a lid and a substrate support. The chambersmay also include a showerhead positioned between the lid and thesubstrate support. A first plasma region may be defined between theshowerhead and the lid, and a second plasma region may be definedbetween the showerhead and the substrate support. The lid and thesubstrate support each may be coupled with a plasma-generating powersource. The showerhead may be electrically coupled with ground, and theshowerhead may include a plate including a first dielectric material.The plate may be characterized by a first surface and a second surfaceopposite the first surface. The plate may define a plurality ofapertures through the plate, and the showerhead may defines a firstannular channel in the first surface of the plate radially outward ofthe plurality of apertures. The showerhead may also include a conductivematerial incorporated with the plate. Exposure of the conductivematerial may be limited to a region radially outward of the firstannular channel.

In some embodiments, the plate may define a second annular channel inthe first surface of the plate. The second annular channel may be formedradially outward from the first annular channel, and the conductivematerial may be embedded within the plate and exposed by the secondannular channel. The second annular channel may be defined within theplate to a greater depth than the first annular channel. The conductivematerial may extend through the plate at a depth within the plategreater than the depth of the first annular channel. The conductivematerial may be exposed by the second annular channel without beingexposed by the first annular channel. The processing chambers may alsoinclude an RF gasket seated within the second annular channel andconfigured to electrically couple the conductive material to ground. Thechambers may also include an elastomeric element seated within the firstannular channel. The conductive material may be disposed on the firstsurface of the plate, and the conductive material may be maintained at afirst radial distance from each aperture of the plurality of apertures.The showerheads may also include a coating that may be a seconddielectric material. The coating may extend across the conductivematerial, and the coating may be maintained at a second radial distancefrom each aperture of the plurality of apertures. The second radialdistance may be less than the first radial distance. The coating may beor include a multilayer coating. The conductive material may be orinclude a perforated foil or mesh.

Such technology may provide numerous benefits over conventional systemsand techniques. For example, the showerheads may operate as a groundelectrode during plasma processing. Additionally, the showerheads maylimit metal bombardment with plasma species during plasma formation.These and other embodiments, along with many of their advantages andfeatures, are described in more detail in conjunction with the belowdescription and attached figures.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the disclosedtechnology may be realized by reference to the remaining portions of thespecification and the drawings.

FIG. 1 shows a top plan view of one embodiment of an exemplaryprocessing system according to some embodiments of the presenttechnology.

FIG. 2A shows a schematic cross-sectional view of an exemplaryprocessing chamber according to some embodiments of the presenttechnology.

FIG. 2B shows a detailed schematic view of a portion of the processingchamber illustrated in FIG. 2A according to some embodiments of thepresent technology.

FIG. 3 shows a bottom plan view of an exemplary showerhead according tosome embodiments of the present technology.

FIG. 4 shows exemplary operations in a method according to someembodiments of the present technology.

FIG. 5A shows a schematic partial top plan view of exemplary showerheadsaccording to some embodiments of the present technology.

FIG. 5B shows a schematic partial cross-sectional view of exemplaryshowerheads according to some embodiments of the present technology.

FIG. 6 shows exemplary operations in a method according to someembodiments of the present technology.

FIGS. 7A-7C show schematic top plan views of exemplary showerheadsaccording to some embodiments of the present technology.

FIG. 7D shows a schematic partial cross-sectional view of exemplaryshowerheads according to some embodiments of the present technology.

FIG. 8 shows exemplary operations in a method according to someembodiments of the present technology.

FIGS. 9A-9B show schematic top plan views of exemplary showerheadsaccording to some embodiments of the present technology.

Several of the figures are included as schematics. It is to beunderstood that the figures are for illustrative purposes, and are notto be considered of scale unless specifically stated to be of scale.Additionally, as schematics, the figures are provided to aidcomprehension and may not include all aspects or information compared torealistic representations, and may include additional or exaggeratedmaterial for illustrative purposes.

In the appended figures, similar components and/or features may have thesame reference label. Further, various components of the same type maybe distinguished by following the reference label by a letter thatdistinguishes among the similar components. If only the first referencelabel is used in the specification, the description is applicable to anyone of the similar components having the same first reference labelirrespective of the letter.

DETAILED DESCRIPTION

Dry etching processes may develop plasma species within certain regionsof a processing region. Different plasma regions may include localregions, or areas proximate a substrate surface, as well as remoteregions, such as in fluidly coupled but physically separated sections ofa processing chamber. Many processing chambers include a number ofdifferent material components defining interior spaces within thechamber. For example, metallic components may be incorporated to operateas electrodes within the chamber, such as for capacitively-coupledplasma operations. Additionally, dielectric materials may be included toseparate electrodes or operate as material coatings.

Showerheads that may operate as plasma electrodes, or may more generallyassist in flow of plasma species, may be contacted and/or otherwiseexposed to plasma effluents. Many etchant materials may interact withthese electrodes, which may strip coatings or bombard exposed regions.As one non-limiting example, in some local or wafer-level plasmaoperations, a showerhead or manifold may operate as a ground electrodeto develop plasma in the substrate processing region, where thesubstrate support or some other component may operate as theplasma-generating electrode. The showerhead operating as the groundelectrode may be bombarded by plasma species, which on exposed metal maycause metallic species to contaminate the substrate, which could causeshorting during operation. Accordingly, some conventional designs mayroutinely exchange the showerhead or coat the showerhead with a materialthat may resist the bombardment.

The coatings used in some conventional designs may operate sufficientlyagainst bombardment, or erosion, but may not sufficiently withstand achemical reaction with plasma effluent species, which may causecorrosion of the coating. Accordingly, these components may routinelyrequire re-coating or replacement. Moreover, many showerheads include anumber of holes for delivering species through the chamber. If thecoatings cannot completely coat every aperture sidewall and all exposedsurfaces, plasma species that may be developed remotely may cause thesame issues as species developed locally. Additionally, if the holes arenot sufficiently small, local plasma may leak through these holesdamaging other upstream components. However, when holes are formedsufficiently small, many line-of-sight coating devices are incapable ofproviding a complete coating within the holes. Hence, many conventionalshowerheads have been incapable of long-term, stable operation aselectrodes.

The present technology overcomes these issues by utilizing dielectric orceramic materials for the showerheads. Typically, ceramic materialscannot be used as electrodes due to their dielectric properties. Thepresent technology incorporates one or more conductive materials withinthe ceramic, which allow the component to operate as an electrode. Theconductive material may be contained within the ceramic or dielectricmaterial in regions exposed to plasma, which may prevent contaminationor bombardment issues described above. By utilizing particular materialsfor the components, showerheads having reduced aperture size may beproduced that afford complete coverage of the conductive material.Additionally, the materials may resist erosion and/or corrosion fromplasma exposure.

Although the remaining disclosure will routinely identify specificetching processes utilizing the disclosed technology, it will be readilyunderstood that the systems and methods are equally applicable todeposition and cleaning processes and chambers as may occur in thedescribed chambers or other chambers. Accordingly, the technology shouldnot be considered to be so limited as for use with any particularetching processes or chambers alone. Moreover, although an exemplarychamber is described to provide foundation for the present technology,it is to be understood that the present technology can be applied tovirtually any semiconductor processing chamber that may allow theoperations described.

FIG. 1 shows a top plan view of one embodiment of a processing system100 of deposition, etching, baking, and curing chambers according toembodiments. In the figure, a pair of front opening unified pods (FOUPs)102 supply substrates of a variety of sizes that are received by roboticarms 104 and placed into a low pressure holding area 106 before beingplaced into one of the substrate processing chambers 108 a-f, positionedin tandem sections 109 a-c. A second robotic arm 110 may be used totransport the substrate wafers from the holding area 106 to thesubstrate processing chambers 108 a-f and back. Each substrateprocessing chamber 108 a-f, can be outfitted to perform a number ofsubstrate processing operations including the dry etch processesdescribed herein in addition to cyclical layer deposition (CLD), atomiclayer deposition (ALD), chemical vapor deposition (CVD), physical vapordeposition (PVD), etch, pre-clean, degas, orientation, and othersubstrate processes.

The substrate processing chambers 108 a-f may include one or more systemcomponents for depositing, annealing, curing and/or etching a dielectricfilm on the substrate wafer. In one configuration, two pairs of theprocessing chambers, e.g., 108 c-d and 108 e-f, may be used to depositdielectric material on the substrate, and the third pair of processingchambers, e.g., 108 a-b, may be used to etch the deposited dielectric.In another configuration, all three pairs of chambers, e.g., 108 a-f,may be configured to etch a dielectric film on the substrate. Any one ormore of the processes described may be carried out in chamber(s)separated from the fabrication system shown in different embodiments. Itwill be appreciated that additional configurations of deposition,etching, annealing, and curing chambers for dielectric films arecontemplated by system 100.

FIG. 2A shows a cross-sectional view of an exemplary process chambersystem 200 with partitioned plasma generation regions within theprocessing chamber. During film etching, e.g., titanium nitride,tantalum nitride, tungsten, silicon, polysilicon, silicon oxide, siliconnitride, silicon oxynitride, silicon oxycarbide, etc., a process gas maybe flowed into the first plasma region 215 through a gas inlet assembly205. A remote plasma system (RPS) 201 may optionally be included in thesystem, and may process a first gas which then travels through gas inletassembly 205. The inlet assembly 205 may include two or more distinctgas supply channels where the second channel (not shown) may bypass theRPS 201, if included.

A cooling plate 203, faceplate 217, ion suppressor 223, showerhead 225,and a substrate support 265, having a substrate 255 disposed thereon,are shown and may each be included according to embodiments. The coolingplate and faceplate may operate as aspects of a lid assembly in someembodiments. The pedestal 265 may have a heat exchange channel throughwhich a heat exchange fluid flows to control the temperature of thesubstrate, which may be operated to heat and/or cool the substrate orwafer during processing operations. The wafer support platter of thepedestal 265, which may include aluminum, ceramic, or a combinationthereof, may also be resistively heated in order to achieve relativelyhigh temperatures, such as from up to or about 100° C. to above or about1100° C., using an embedded resistive heater element.

The faceplate 217 may be pyramidal, conical, or of another similarstructure with a narrow top portion expanding to a wide bottom portion.The faceplate 217 may additionally be flat as shown and include aplurality of through-channels used to distribute process gases. Plasmagenerating gases and/or plasma excited species, depending on use of theRPS 201, may pass through a plurality of holes, shown in FIG. 2B, infaceplate 217 for a more uniform delivery into the first plasma region215.

Exemplary configurations may include having the gas inlet assembly 205open into a gas supply region 258 partitioned from the first plasmaregion 215 by faceplate 217 so that the gases/species flow through theholes in the faceplate 217 into the first plasma region 215. Structuraland operational features may be selected to prevent significant backflowof plasma from the first plasma region 215 back into the supply region258, gas inlet assembly 205, and fluid supply system 210. The faceplate217, or a conductive top portion of the chamber, and showerhead 225 areshown with an insulating ring 220 located between the features, whichallows an AC potential to be applied to the faceplate 217 relative toshowerhead 225 and/or ion suppressor 223. The insulating ring 220 may bepositioned between the faceplate 217 and the showerhead 225 and/or ionsuppressor 223 enabling a capacitively coupled plasma (CCP) to be formedin the first plasma region. A baffle (not shown) may additionally belocated in the first plasma region 215, or otherwise coupled with gasinlet assembly 205, to affect the flow of fluid into the region throughgas inlet assembly 205.

The ion suppressor 223 may comprise a plate or other geometry thatdefines a plurality of apertures throughout the structure that areconfigured to suppress the migration of ionically-charged species out ofthe first plasma region 215 while allowing uncharged neutral or radicalspecies to pass through the ion suppressor 223 into an activated gasdelivery region between the suppressor and the showerhead. Inembodiments, the ion suppressor 223 may comprise a perforated plate witha variety of aperture configurations. These uncharged species mayinclude highly reactive species that are transported with less reactivecarrier gas through the apertures. As noted above, the migration ofionic species through the holes may be reduced, and in some instancescompletely suppressed. Controlling the amount of ionic species passingthrough the ion suppressor 223 may advantageously provide increasedcontrol over the gas mixture brought into contact with the underlyingwafer substrate, which in turn may increase control of the depositionand/or etch characteristics of the gas mixture. For example, adjustmentsin the ion concentration of the gas mixture can significantly alter itsetch selectivity, e.g., SiNx:SiOx etch ratios, Si:SiOx etch ratios, etc.In alternative embodiments in which deposition is performed, it can alsoshift the balance of conformal-to-flowable style depositions fordielectric materials.

The plurality of apertures in the ion suppressor 223 may be configuredto control the passage of the activated gas, i.e., the ionic, radical,and/or neutral species, through the ion suppressor 223. For example, theaspect ratio of the holes, or the hole diameter to length, and/or thegeometry of the holes may be controlled so that the flow ofionically-charged species in the activated gas passing through the ionsuppressor 223 is reduced. The holes in the ion suppressor 223 mayinclude a tapered portion that faces the plasma excitation region 215,and a cylindrical portion that faces the showerhead 225. The cylindricalportion may be shaped and dimensioned to control the flow of ionicspecies passing to the showerhead 225. An adjustable electrical bias mayalso be applied to the ion suppressor 223 as an additional means tocontrol the flow of ionic species through the suppressor.

The ion suppressor 223 may function to reduce or eliminate the amount ofionically charged species traveling from the plasma generation region tothe substrate. Uncharged neutral and radical species may still passthrough the openings in the ion suppressor to react with the substrate.It should be noted that the complete elimination of ionically chargedspecies in the reaction region surrounding the substrate may not beperformed in embodiments. In certain instances, ionic species areintended to reach the substrate in order to perform the etch and/ordeposition process. In these instances, the ion suppressor may help tocontrol the concentration of ionic species in the reaction region at alevel that assists the process.

Showerhead 225 in combination with ion suppressor 223 may allow a plasmapresent in first plasma region 215 to avoid directly exciting gases insubstrate processing region 233, while still allowing excited species totravel from chamber plasma region 215 into substrate processing region233. In this way, the chamber may be configured to prevent the plasmafrom contacting a substrate 255 being etched. This may advantageouslyprotect a variety of intricate structures and films patterned on thesubstrate, which may be damaged, dislocated, or otherwise warped ifdirectly contacted by a generated plasma. Additionally, when plasma isallowed to contact the substrate or approach the substrate level, therate at which oxide species etch may increase. Accordingly, if anexposed region of material is oxide, this material may be furtherprotected by maintaining the plasma remotely from the substrate.

The processing system may further include a power supply 240electrically coupled with the processing chamber to provide electricpower to the faceplate 217, ion suppressor 223, showerhead 225, and/orpedestal 265 to generate a plasma in the first plasma region 215 orprocessing region 233. The power supply may be configured to deliver anadjustable amount of power to the chamber depending on the processperformed. Such a configuration may allow for a tunable plasma to beused in the processes being performed. Unlike a remote plasma unit,which is often presented with on or off functionality, a tunable plasmamay be configured to deliver a specific amount of power to the plasmaregion 215. This in turn may allow development of particular plasmacharacteristics such that precursors may be dissociated in specific waysto enhance the etching profiles produced by these precursors.

A plasma may be ignited either in chamber plasma region 215 aboveshowerhead 225 or substrate processing region 233 below showerhead 225.Plasma may be present in chamber plasma region 215 to produce theradical precursors from an inflow of, for example, a fluorine-containingprecursor or other precursor. An AC voltage typically in the radiofrequency (RF) range may be applied between the conductive top portionof the processing chamber, such as faceplate 217, and showerhead 225and/or ion suppressor 223 to ignite a plasma in chamber plasma region215 during deposition. An RF power supply may generate a high RFfrequency of 13.56 MHz but may also generate other frequencies alone orin combination with the 13.56 MHz frequency.

FIG. 2B shows a detailed view 253 of the features affecting theprocessing gas distribution through faceplate 217. As shown in FIGS. 2Aand 2B, faceplate 217, cooling plate 203, and gas inlet assembly 205intersect to define a gas supply region 258 into which process gases maybe delivered from gas inlet 205. The gases may fill the gas supplyregion 258 and flow to first plasma region 215 through apertures 259 infaceplate 217. The apertures 259 may be configured to direct flow in asubstantially unidirectional manner such that process gases may flowinto processing region 233, but may be partially or fully prevented frombackflow into the gas supply region 258 after traversing the faceplate217.

The gas distribution assemblies such as showerhead 225 for use in theprocessing chamber section 200 may be referred to as dual channelshowerheads (DCSH) and are additionally detailed in the embodimentsdescribed in FIG. 3. The dual channel showerhead may provide for etchingprocesses that allow for separation of etchants outside of theprocessing region 233 to provide limited interaction with chambercomponents and each other prior to being delivered into the processingregion.

The showerhead 225 may comprise an upper plate 214 and a lower plate216. The plates may be coupled with one another to define a volume 218between the plates. The coupling of the plates may be so as to providefirst fluid channels 219 through the upper and lower plates, and secondfluid channels 221 through the lower plate 216. The formed channels maybe configured to provide fluid access from the volume 218 through thelower plate 216 via second fluid channels 221 alone, and the first fluidchannels 219 may be fluidly isolated from the volume 218 between theplates and the second fluid channels 221. The volume 218 may be fluidlyaccessible through a side of the gas distribution assembly 225.

FIG. 3 is a bottom view of a showerhead 325 for use with a processingchamber according to embodiments. Showerhead 325 may correspond with theshowerhead 225 shown in FIG. 2A. Through-holes 365, which show a view offirst fluid channels 219, may have a plurality of shapes andconfigurations in order to control and affect the flow of precursorsthrough the showerhead 225. Small holes 375, which show a view of secondfluid channels 221, may be distributed substantially evenly over thesurface of the showerhead, even amongst the through-holes 365, and mayhelp to provide more even mixing of the precursors as they exit theshowerhead than other configurations.

Turning to FIG. 4 is shown exemplary operations in a method 400 forproducing a showerhead according to some embodiments of the presenttechnology. As described above, some showerheads or chamber componentsthat may operate as an electrode during plasma operation, includingeither a plasma-generating electrode or a ground electrode, may beformed of a ceramic or dielectric material, and may include a conductivematerial incorporated with or within the dielectric. Showerheadsdiscussed throughout the present disclosure may be used as any of thecomponents described previously including faceplates, ion suppressors,gas distribution assemblies, or other showerheads or manifolds used inchambers as described above, or any other chamber that may utilize sucha component in plasma operations. Accordingly, although certain designswill be illustrated, it is to be understood that many differentconfigurations are equally encompassed by the present technology.

In some embodiments the conductive material may be incorporated withinor embedded within the showerhead during formation operations. Becausesome of the components described may be ceramic, the components may beformed in molding operations in which heat and/or pressure may be usedto form the components. For example, sintering may be used to form theshowerheads from one or more molded green bodies. In some embodiments ofmethod 400 for producing a showerhead, green bodies may be formed inoperation 405, such as two green bodies that may come together and besintered to produce an exemplary showerhead. The green bodies may bedisc-shaped, or may be characterized by any other shape so as to beseated in an exemplary processing chamber. The green bodies may bemolded to include one or more plug holes or studs that may allow the twocomponents to be coupled prior to a firing operation, and the bodies mayinclude a few larger sets, or may include a number of studs and/or plugholes distributed between the bodies.

Once the green bodies have been formed, a conductive material may beapplied or seated on one of the green bodies at operation 410. Theconductive material may be a mesh, foil, or coating applied to one orboth of the green bodies within a particular area as will be describedbelow. The conductive material may be pre-formed to include apertures,which may be in a pattern similar to apertures that may be later drilledinto the showerhead to provide gas flow. Exemplary showerheads mayinclude tens, hundreds, or thousands of apertures, and thus theconductive material positioning may be performed to ensure that apertureformation may not expose the conductive material. As explained above,conductive material that may be exposed to plasma effluents may beetched, sputtered, or otherwise damaged by the plasma. Accordingly,development of exemplary showerheads may be performed to expressly limitexposure of the conductive material in regions where plasma exposure mayoccur.

For example, apertures may be formed or drilled through the completedceramic. Accordingly, the conductive material may be formed or appliedto the green bodies to include apertures that will allow the showerheadapertures to be produced without exposing the conductive material. Insome embodiments, the conductive material itself may include apertureswhen it is positioned on the green bodies. For example, a foil may beproduced that includes the apertures to be defined. Additional aperturesmay correspond to plug holes or studs for the green bodies, which mayprovide a locating function for the foil apertures for subsequentmachining. As another example, because the green bodies may be molded,plug holes and studs may be distributed about the green body molds tocorrespond to where apertures may be produced, which may limit shiftingduring the firing operation. For example, a mesh or foil may bepress-fit to the green body about the studs. Mesh tines may be separatedabout the studs, which may allow a consistent application of theconductive material across the mold, and limit sharp edges from cutting.

Once the conductive material has been applied, the green bodies may befired to produce a showerhead in operation 415. The firing may includethe application of heat and/or pressure to produce the ceramiccomponent. Such a firing may include multiple operations includinglow-temperature heating followed by high-temperature heating, forexample. After the component has been formed, the showerhead may bepatterned in operation 420, which may provide apertures, channels, andother features during machining to produce a final showerhead. Theseproduced showerheads may define a number of apertures in an interiorregion of the showerhead that may not expose the conductive materialcontained across the showerhead. Accordingly, the showerhead may operateas both a flow distribution component, as well as an electrode, whilelimiting or preventing conductive material from being exposed within thechamber processing regions.

FIG. 5A shows a schematic partial top plan view of exemplary showerhead500 according to some embodiments of the present technology. Theshowerhead may include a dielectric plate 505, which may be a ceramic,for example, and the showerhead may also include an incorporatedconductive material 510. FIG. 5B shows a schematic partialcross-sectional view of exemplary showerhead 500 according to someembodiments of the present technology, and may be considered with FIG.5A to illustrate various features of the showerhead. As noted above,showerhead 500 is only one exemplary configuration of componentsencompassed by the present technology. Showerhead 500 illustratesfeatures that may be included with various showerheads according to thepresent technology, but is not intended to limit other designs similarlyencompassed. Showerhead 500 may be any of the manifolds discussedpreviously, and may be a single piece component, or in some embodimentsmay be one of a combination of components, such as to produce a gasdistribution assembly as previously described. Showerhead 500 may beincluded in a semiconductor processing chamber as previously described,or any other processing chamber or system in embodiments of the presenttechnology.

As shown, dielectric plate 505 may be a ceramic plate as formed bymethod 400 discussed above, or by any other method, and may includeincorporated conductive material 510. Dielectric plate 505 may include afirst surface 507 and a second surface 509, which may be opposite thefirst surface 507. Dielectric plate 505 may define a number of apertures515 through the plate, which extend from the first surface 507 throughthe second surface 509, and may provide paths for precursors through theshowerhead. Apertures 515 may be formed through the showerhead aftersintering as described above, and after conductive material 510 has beenincorporated. The apertures 515 may not contact or expose conductivematerial 510 in some embodiments. As illustrated, conductive material510 may extend about some or all of apertures 515. As shown in FIG. 5B,conductive material 510 may maintain a separation or gap 518 about eachaperture to ensure that the apertures do not expose the conductivematerial when formed.

Dielectric plate 505 may define one or more channels as well as one ormore recessed features that may be machined subsequent incorporation ofthe conductive material 510. During sintering operations, materialproperties and characteristics may change, which may distribute theconductive material, foil, or mesh. For example, prior to firing, anexact depth of the conductive material 510 within the dielectric platemay be known. However, subsequent firing, this location may changeslightly. Radial gap 518 may ensure that any lateral movement may beaccommodated during aperture formation. However, because the conductivematerial may be only a few hundred nanometers in thickness in someembodiments, although any thickness may be used, slight changes in depthmay challenge locating the conductive material for electrode coupling aswell as for feature formation. For example, some exemplary showerheadsmay include recess 520 formed at an interior region of second surface509. If the location of conductive material 510 has shifted duringfiring, conductive material 510 may inadvertently be exposed when recess520 is formed. The present technology may perform locating in a numberof ways to limit or prevent exposure of the conductive material in thedielectric plate.

Dielectric plate 505 may define a first annular channel 525 in the firstsurface 507 of dielectric plate 505. The first annular channel 525 mayextend about the plurality of apertures 515, and may define an interiorregion 526 of the showerhead. First annular channel 525 may beconfigured to seat an o-ring or elastomeric element 527 for producing aseal during vacuum operations. Accordingly, interior region 526 may be aportion of the showerhead 500 that may be exposed within the chamber toany processing being performed, such as plasma processing, for example.In some embodiments, conductive material 510 may not be exposed anywherein interior region 526, including where apertures 515 are formed.

Because conductive material 510 may be coupled as an electrode, theconductive material may be exposed in at least one location to providecoupling. In some embodiments, dielectric plate 505 may define a secondannular channel 530 in the first surface 507 of dielectric plate 505.Second annular channel 530 may be configured to seat an RF gasket 533,or any other conductive connection that may contact conductive material510. Second annular channel 530 may be formed radially outward from thefirst annular channel 525, and thus may be positioned in a locationexternal from the processing regions of the chamber. Accordingly, secondannular channel 530 may not be exposed to events occurring within thechamber, and may not be exposed to any plasma effluents, for example.

Conductive material 510 may be exposed in at least one location withinsecond annular channel 530, and may be exposed in multiple locationswithin second annular channel 530. Because second annular channel 530may be formed radially outward of first annular channel 525, conductivematerial 510 may extend past first annular channel 525. To preventexposure of the conductive material in first annular channel 525, secondannular channel 530 may be defined within the dielectric plate 505 to agreater depth than the first annular channel 525. Hence, as shown inFIG. 5B, conductive material 510 may extend past first annular channel525 at a depth below first annular channel 525, which may preventexposure of the conductive material at the first annular channel. WhenRF gasket 533 is seated within second annular channel 530, the gasketmay contact conductive material 510 exposed within the channel, whichmay provide a path to operate the conductive material as an electrodewithin the chamber.

As noted above, the conductive material may be located within thedielectric plate to ensure the depth of the conductive material isknown. Accordingly, in some embodiments second annular channel 530 maybe machined or formed prior to other features of the showerhead.Conductive material 510 may extend completely to an outer region of theshowerhead, or the conductive material 510 may include one or more wingsor tabs 535 extending from a more uniform coverage in interior region526 into an exterior region where exterior channel 530 may be formed.One or more locating holes or grooves may be formed down through theexterior region to locate the exact depth of the conductive material510, such as between tabs 535 when included, for example. Once known,second annular channel 530 may be formed to fully expose conductivematerial 510 within the channel. Because the conductive material mayextend about the showerhead, and RF gasket 533 or other electroniccoupling may extend about the showerhead as well, any perforation of theconductive material in the exterior region during locating may notimpact operation of the conductive material as an electrode due to themultiple points of contact about the showerhead.

Dielectric plate 505 may include any number of materials that mayprotect against bombardment from plasma species, and may be inert toplasma effluents, such as halogen-containing plasma effluents. Forexample, dielectric plate 505 may include oxides or nitrides of anynumber of metals including aluminum, yttrium, zirconium, silicon, orother elements or combinations. The conductive material may be anynumber of conductive materials that may operate or be used as anelectrode, and may include aluminum, tungsten, molybdenum, tantalum,platinum, titanium, vanadium, or any other material including alloys ofany of these or other conductive materials. While some embodiments asdescribed below may not include sintering operations, when showerheadsmay be developed according to method 400, the firing temperatures may bewell over 1,000° C. Accordingly, lower melting temperature metals, suchas aluminum for example, may not be suitable candidates. Additionally,the ceramic material and conductive material may be selected to producean amount of matching about the firing temperature to controlexpansion/contraction during the firing.

The dielectric plate may also be formed to control an amount of porosityof the showerhead produced. Because the components may be operatingunder vacuum conditions, porosity may be maintained relatively low tolimit effects with vacuum conditions or outgassing with the showerhead.Similarly, components characterized by higher porosity may besusceptible to increased absorption of plasma species, which may requireincreased seasoning before processing is performed, for example.Accordingly, in some embodiments porosity of the material used fordielectric plate 505 may be limited below about 5%, and in someembodiments may be limited below or about 3%, below or about 2%, belowor about 1%, below or about 0.9%, below or about 0.8%, below or about0.7%, below or about 0.6%, below or about 0.5%, below or about 0.4%,below or about 0.3%, below or about 0.2%, below or about 0.1%, or less.

When apertures are formed prior to coating, such as with many metalliccomponents, smaller apertures may not be feasible, or complete coatingmay not occur. However, the larger the apertures are formed tofacilitate coating, the more likely plasma leakage is to occur. Thepresent technology overcomes these issues because the apertures may onlyextend through dielectric plate 505 without contacting conductivematerial 510. Thus, because the issue with coating is overcome by usingthe ceramic material where aperture formation may not expose conductivematerial, smaller apertures may be drilled than in conventionalmaterials where subsequent coating may be performed. Accordingly, insome embodiments apertures 515 may be characterized by a diameter ofless than or about 10 mm, and in some embodiments may be characterizedby a diameter of less than or about 9 mm, less than or about 8 mm, lessthan or about 7 mm, less than or about 6 mm, less than or about 5 mm,less than or about 4 mm, less than or about 3 mm, less than or about 2mm, less than or about 1 mm, or less. The aperture sizes may impact gap518 that may be maintained, along with the amount of travel that may beexperienced during formation. Accordingly, gap 518, which may be aradial gap, may extend less than or about 5 mm about each aperture, andin some embodiments may extend less than or about 4 mm, less than orabout 3 mm, less than or about 2 mm, less than or about 1 mm, less thanor about 0.5 mm, or less about each aperture, which may ensure theconductive material is not exposed during formation of the apertures.

Showerheads according to the present technology may also include one ormore coatings to limit or prevent exposure of conductive material to theinterior chamber environment. FIG. 6 shows exemplary operations in amethod 600 according to some embodiments of the present technology.Method 600 may produce showerheads similar to those discussed above, aswell as other chamber manifolds or diffusers as previously described.Method 600 may include any of the operations of method 400 for producinga dielectric component, and showerheads produced may include any of thematerials, properties, or characteristics as previously described.

Method 600, similar to method 400, may include one or more optionaloperations, which may or may not be specifically associated with someembodiments of methods according to the present technology. For example,many of the operations are described in order to provide a broader scopeof the structural formation, but are not critical to the technology, ormay be performed by alternative methodology as will be discussed furtherbelow. Method 600 describes operations shown schematically in top planviews of exemplary showerheads 700 in FIGS. 7A-7C, the illustrations ofwhich will be described in conjunction with the operations of method600. Showerhead 700 may similarly be incorporated in any processingchamber in embodiments of the present technology. It is to be understoodthat FIG. 7 illustrates only general schematic views for illustrativepurposes, and exemplary showerheads may contain any number of aperturesor structural elements as will be described.

Method 600 may include etching a plate to produce apertures and otherfeatures at operation 605. For example, apertures may be drilled througha ceramic or dielectric plate, which may have any of the features,materials, or characteristics of showerhead 500 described above. Asillustrated in FIG. 7A, apertures 715 may be drilled or formed through adielectric plate 705 when producing showerhead 700. A mesh, foil,printing, or spray of a conductive or metal material may be applied tothe plate on one or more surfaces at operation 610. The conductivematerials may be any of the conductive materials as previouslydescribed, and may be positioned or formed on one or more surfaces, suchas on a first surface of the showerhead. FIG. 7B shows the formation ofconductive material 710 on a first surface of showerhead 700. Asillustrated, conductive material 710 may extend across the first surfaceof the showerhead, although a gap 712 may be maintained about eachaperture. For example, the conductive material may be maintained awayfrom the apertures a first radial distance from each aperture, which maycorrespond to any gap distances described above. The gap 712 may performa similar feature of ensuring that the conductive material may not beexposed, although the gap may also provide space for a subsequentlyadded coating as will be described below. The gap may be included inpre-formed conductive materials, or another masking operation may beperformed to produce the gap.

The formed apertures may then be masked at optional operation 615. Themasking may be performed just about the holes and extend a limiteddistance radially or laterally about each aperture. A coating may thenbe applied at operation 620 to cover conductive material 710. After thecoating has been applied, the mask may be removed in optional operation625. The coating may also be a dielectric material, and may be a seconddielectric material to a first dielectric material of the plate. FIG. 7Cillustrates a showerhead subsequent application of the coating 720 toextend across conductive material 710. Coating 720 may also be appliedto maintain a gap 722 from each aperture 715, and the coating 720 may bemaintained a second radial distance from each aperture. In someembodiments the second radial distance may be less than the first radialdistance, which may ensure that coating 720 completely covers conductivematerial 710.

FIG. 7C also shows that conductive material 710 may be exposed in one ormore positions along an exterior or radial edge 725 of showerhead 700.The exposure may occur radially outward of an annular channel 730, whichmay be where an elastomeric element may be seated. The annular channel730 may be defined radially outward of the apertures, and may define aboundary between an interior region of the showerhead that may beexposed within a chamber, and the exterior region which may not beexposed to chamber processing. Although shown in FIG. 7C, it is to beunderstood that the channel may have been formed previously duringaperture formation to ensure continuity of the material to allowoperation as an electrode. Accordingly, where the conductive material isexposed at region 725 may allow coupling for electrode operation, whilelimiting or preventing exposure of the conductive material within thechamber environment. In some embodiments a hybrid coating may beapplied, and may include a first coating applied over the entireshowerhead, while a second thicker coating, such as a second layer asdescribed below, may not be applied to an edge region. The thinnercoating may allow electrical connections through the coating because ofthe thickness, which may not fully insulate from electrical contact,although protecting from some plasma effluents. This option may provideadditional flexibility during manufacturing in some embodiments.

FIG. 7D shows a schematic partial cross-sectional view of exemplaryshowerheads according to some embodiments of the present technology, andmay illustrate another view of showerhead 700, for example. The figureshows a portion of the showerhead including dielectric plate 705,conductive material 710, and coating 720 as they may be formed aboutaperture 715. Aperture 715 is shown with a chamfered edge, but thefigure is merely to illustrate that any aperture design may beaccommodated with any of the present technology, and showerheads 500,700, or any other showerhead produced may be characterized by anyaperture profile.

FIG. 7D illustrates how conductive material 710 may be formed across afirst surface 707 of plate 705. A second surface 709 opposite the firstsurface may not include conductive material or coating 720, although insome embodiments the second surface may also include one or more of thematerials. For example, depending on the orientation of the showerheador chamber component, one side of the component may be exposed more tobombardment, while one side may be exposed more to chemically reactiveplasma effluents, and the coating may be applied accordingly, althoughas noted the coating may be applied to either or both sides of theshowerhead. As illustrated, conductive material 710 may be maintainedaway from the aperture 715 to a first distance or gap 712. Coating 720may be applied over the conductive material 710 and may be applied to asecond distance or gap 722, which may be less than the first gap.Accordingly, conductive material 710 may be completely covered in aninterior region of the showerhead in embodiments of the presenttechnology.

Dielectric material for both the plate and the coating may be any of thematerials previously described, and the conductive material may also beany of the previously noted materials. Additionally, coating 720 may bea type of hybrid or multilayer coating in some embodiments. For example,a first layer of coating 720 may be included to limit exposure of theconductive material to a second layer of coating, which may limitoxidation or other effects on the conductive material, for example.

Chambers according to some embodiments of the present technology may beused to perform modification operations in which a bias plasma may beformed in a substrate processing region. This operation may be aphysical bombardment of structures on a substrate, and may utilize inertor less reactive precursors. Additionally, a reactive etch may beperformed by producing reactive plasma effluents in a remote region. Theprecursors may include halogen precursors, which may be configured toremove modified material from a substrate. Accordingly, components ofthe chamber, such as showerheads described, may be exposed to bothchemically reactive plasma effluents, such as fluorine, chlorine, orother halogen-containing effluents, as well as ions produced in the biasplasma used for physical modification. For example, exemplaryshowerheads may be exposed to both plasma effluents, such as bias plasmaeffluents contacting the surface facing the substrate and withinapertures, as well as reactive effluents proceeding through aperturesbefore interacting with a substrate. Other components described abovemay also be exposed to one or both plasma effluents, including frombackstreaming plasma effluents. While conventional components maydegrade due to conductive component exposure to the plasma materials,showerheads of the present technology may limit or prevent anyconductive material exposure while still operating as plasma electrodes.

The plasma effluents may produce differing effects on the chambercomponents. For example, ions may be at least partially filtered by theshowerhead from the chemically reactive plasma effluents producedremotely. However, the reactive effluents, such as fluorine-containingeffluents, for example, may cause corrosion of exposed materials, suchas by forming aluminum fluoride in conventional component designs. Overtime, this process may corrode exposed metallic components, requiringreplacement. Additionally, plasma species formed from a bias plasma inthe substrate processing region may impact components causing physicaldamage and sputtering that may erode components over time. Accordingly,any of the described components may be susceptible to chemical corrosionas well as physical erosion from plasma effluents produced within one ormore regions of the chamber.

Corrosion may be controlled in some ways by forming a coating 720 overmaterials, or using specific materials for the coating. For example,while aluminum may corrode from exposure to fluorine-containing plasmaeffluents, aluminum oxide, or other platings or coatings, may notcorrode on contact with plasma effluents. Accordingly, any of thedescribed components may be coated or protected by anodization,oxidation, atomic layer deposition, chemical vapor deposition, plasmaspray, electroless nickel plating, electroplated nickel, bariumtitanate, or any other material that may protect exposed conductivematerials, such as aluminum, molybdenum, platinum, or any of thepreviously noted materials, from chemical corrosion. Similarly, erosionmay be controlled in some ways by forming a coating over materials orusing certain materials for the base plate 705. For example, highperformance materials such as yttrium oxide, which may or may notinclude additional materials including aluminum or zirconium, forexample, may protect the component from physical damage caused by biasplasma effluents. Damage to components may still occur, however, when astructure may be contacted by both corrosive plasma effluents as well aserosive plasma effluents. Accordingly, coating 720 may include multiplematerials as noted, and base plate 705 may include an additional coatingas well. The materials may be the same, different, or combinations inembodiments. For example, coating 720 may include a plasma spray yttriumoxide in some embodiments along with any of the other materials noted toenhance resistance to plasma effluents.

Additionally, a first layer of a hybrid coating 720 may extendconformally across conductive material 710. As explained previously, thefirst layer may be a corrosion resistant layer, configured to protectthe conductive material from reactive etchants, includinghalogen-containing effluents or etchant materials. The first layer maybe or include an anodization, electroless nickel plating, electroplatednickel, aluminum oxide, or barium titanate in embodiments. Due to theformation process for corrosion resistant coatings, complete coverage ofthe conductive material may be achieved. A depth of coverage may be lessthan or about 25 μm, and may be less than or about 20 μm, less than orabout 15 μm, less than or about 10 μm, less than or about 5 μm, lessthan or about 3 μm, less than or about 1 μm, less than or about 750 nm,less than or about 500 nm, less than or about 250 nm, less than or about100 nm, less than or about 50 nm, or less. Because the time to achieveincreased thickness may be relatively long in some embodiments, thecoating thickness may be between about 100 nm and about 300 nm in someembodiments. In embodiments where the thickness of the first layer maybe greater than or about 3 μm or about 5 μm, a second layer may not beincluded.

A second layer of the hybrid coating may also be included externally tothe first layer. The second layer may include yttrium oxide, or otherhigh performance materials, such as e-beam coating or yttrium oxideincluding aluminum, zirconium, or other materials. The second layer mayextend at least partially across the first surface 707, and may extendacross a plasma-facing surface of the component. The second layer ofhybrid coating may be characterized by a thickness of less than or about25 μm, and may be characterized by a thickness of less than or about 20μm, less than or about 15 μm, less than or about 10 μm, less than orabout 5 μm, less than or about 1 μm, less than or about 750 nm, lessthan or about 500 nm, less than or about 300 nm, less than or about 100nm, or less in some embodiments.

As previously discussed, a masking operation may be performed prior toapplying the coating 720. Because the coating may be applied by a spraymechanism in some embodiments, delivery through apertures that may besized as previously noted may be difficult. If masking is not performed,the coating may not form a complete layer, and pitting formed frominconsistent coating may occur, which may facilitate removal of thecoating during processing over time, and limit repeatability ofapplication. Accordingly, masking may be performed in some embodimentswhere this may be an issue, and which may limit the coating to beexpressly along the conductive material and first surface of the plate.

The plate 705 and/or conductive material 710 may be textured in someembodiments before formation of either or both of the first layer or thesecond layer of the coating, if two layers are used. For example,coatings may have improved adhesion to textured surfaces. In someembodiments, the texturing may be performed to a depth up to or greaterthan either or both layer depths of the hybrid coating. For example,prior to coating a first layer, or between the first and second layercoatings, the plate and/or conductive material may be textured viamachining, bead or other blasting techniques, or other roughening ortexturing operations. The texturing may be performed to a depth of atleast about 50 nm, and may be performed to a depth of at least about 100nm, at least about 250 nm, at least about 500 nm, at least about 750 nm,at least about 1 μm, at least about 3 μm, at least about 5 μm, or more,although the texturing may not extend to a depth greater than theoverall thickness of the materials to limit exposure of underlyingmaterials, and ensure coverage.

FIG. 8 shows exemplary operations in a method 800 according to someembodiments of the present technology. Method 800 may include avariation on the showerhead formation discussed above with method 600.The method will be described with reference to FIGS. 9A-9B, which showschematic top plan views of exemplary showerhead 900 according to someembodiments of the present technology. Method 800 may differ from method600 in that apertures may be formed subsequently to coating in method800. For example, method 800 may begin at operation 805 by forming amask over a dielectric plate where apertures may be subsequentlydrilled. After masking, a conductive mesh, foil, or coating may beapplied at operation 810, which may be performed by a number ofpreviously noted techniques including metal printing or metaldeposition, and which may occur as previously described, and maymaintain a gap distance where the apertures will subsequently be formed.A coating may be applied over the conductive material at operation 815,which may maintain a second gap as discussed previously.

FIG. 9A may illustrate an exemplary showerhead subsequent coating atoperation 815. As illustrated, showerhead 900 may resemble theshowerhead discussed with FIG. 7, although apertures may not be formedthrough the plate 905. Mask material may be removed at operation 820,and then apertures may be machined through the plate at operation 825.As shown in FIG. 9B, the final showerhead may resemble the finalshowerhead of FIG. 7, although the apertures 915 were formed subsequentto coating.

Showerheads according to embodiments of the present technology mayprovide improved corrosion and erosion resistance over conventionalshowerheads that may be based on a conductive base material. Byincorporating a conductive material with or within ceramic or otherdielectric materials as described, operation as an electrode may stillbe afforded, while allowing reduced aperture sizes and improvedcoverage, including complete coverage, of conductive materials withinthe processing chamber.

In the preceding description, for the purposes of explanation, numerousdetails have been set forth in order to provide an understanding ofvarious embodiments of the present technology. It will be apparent toone skilled in the art, however, that certain embodiments may bepracticed without some of these details, or with additional details.

Having disclosed several embodiments, it will be recognized by those ofskill in the art that various modifications, alternative constructions,and equivalents may be used without departing from the spirit of theembodiments. Additionally, a number of well-known processes and elementshave not been described in order to avoid unnecessarily obscuring thepresent technology. Accordingly, the above description should not betaken as limiting the scope of the technology. Additionally, methods orprocesses may be described as sequential or in steps, but it is to beunderstood that the operations may be performed concurrently, or indifferent orders than listed.

Where a range of values is provided, it is understood that eachintervening value, to the smallest fraction of the unit of the lowerlimit, unless the context clearly dictates otherwise, between the upperand lower limits of that range is also specifically disclosed. Anynarrower range between any stated values or unstated intervening valuesin a stated range and any other stated or intervening value in thatstated range is encompassed. The upper and lower limits of those smallerranges may independently be included or excluded in the range, and eachrange where either, neither, or both limits are included in the smallerranges is also encompassed within the technology, subject to anyspecifically excluded limit in the stated range. Where the stated rangeincludes one or both of the limits, ranges excluding either or both ofthose included limits are also included.

As used herein and in the appended claims, the singular forms “a”, “an”,and “the” include plural references unless the context clearly dictatesotherwise. Thus, for example, reference to “a precursor” includes aplurality of such precursors, and reference to “the layer” includesreference to one or more layers and equivalents thereof known to thoseskilled in the art, and so forth.

Also, the words “comprise(s)”, “comprising”, “contain(s)”, “containing”,“include(s)”, and “including”, when used in this specification and inthe following claims, are intended to specify the presence of statedfeatures, integers, components, or operations, but they do not precludethe presence or addition of one or more other features, integers,components, operations, acts, or groups.

1. A semiconductor processing chamber showerhead comprising: a platecomprising a first dielectric material, the plate characterized by afirst surface and a second surface opposite the first surface, whereinthe plate defines a plurality of apertures through the plate; aconductive material disposed on the first surface of the plate, whereinthe conductive material is maintained at a first radial distance fromeach aperture of the plurality of apertures; and a coating comprising asecond dielectric material, wherein the coating extends across theconductive material, and wherein the coating is maintained at a secondradial distance from each aperture of the plurality of apertures,wherein the second radial distance is less than the first radialdistance.
 2. The semiconductor processing chamber showerhead of claim 1,wherein the conductive material is exposed at a radial edge of theshowerhead to provide electrical coupling of the showerhead.
 3. Thesemiconductor processing chamber showerhead of claim 2, wherein theshowerhead defines an annular channel in the first surface of the plateradially outward of the plurality of apertures, and radially inward ofthe exposed conductive material at the radial edge of the showerhead. 4.The semiconductor processing chamber showerhead of claim 1, wherein thecoating comprises a multilayer coating.
 5. The semiconductor processingchamber showerhead of claim 1, wherein the first dielectric material andthe second dielectric material comprise different materials.
 6. Thesemiconductor processing chamber showerhead of claim 1, wherein theconductive material comprises a perforated foil or mesh.